1. Field of the Invention
The present invention relates to an automatic transmission for an automobile and, more particularly, to an automatic transmission using a gear type transmission.
2. Description of the related Art
There is an increasing demand for an automobile having an automatic transmission, and a torque converter is often used at present for the demand. Although various improvements are added to the torque converter so far, however, it is well known that it has a higher fuel consumption than a gear type transmission because of a lower power transmission efficiency. In order to solve this problem, automatic transmission systems using the gear type transmission are studied. One of these systems is disclosed in the papers of the international conference held at Detroit, in February, 1984, "Microcomputer Mechanical Clutch and Transmission Control", Watanabe et al., SAE 840055, in which the clutch and the throttle valve must be operated at a speed change, i.e. the gear shift of the transmission. In the method which is disclosed in "Automation of Mechanical Transmission" (Nagaoka et al.) written down in "Preliminary Reports 822" of Seminars of Association of Automotive Technique, not the clutch but the throttle valve is operated at a speed change to synchronize the input and output shafts of the transmission in the revolutions per minute thereby to mesh the gears. Since, when the gears are to be meshed, the rotational synchronism almost depends on the effect of operating the throttle valve, however, it takes relatively long time for the completion of the rotational synchronism of the input shaft with the output shaft. Any of the concepts disclosed, therefore, has a defect that the time for the gear shift operation of the transmission is elongate to make the running speed liable to fluctuate.